The reaction generates the building blocks of proteins and DNA: amino acids and nucleic acids.
Four billion years ago, the Earth looked very different than it does today. It was devoid of life and covered by a vast ocean. Over the course of millions of years, life emerged in that primordial soup. For a long time, researchers have theorized how molecules came together to spark this transition. Now, scientists at Scripps Research have discovered a new set of chemical reactions that use ammonia, cyanide, and carbon dioxide—all thought to be common on the early Earth—to generate amino acids and nucleic acids, the building blocks of proteins and DNA.
“We’ve come up with a new paradigm to explain this shift from prebiotic to biotic chemistry,” says Ramanarayanan Krishnamurthy, PhD, and an associate professor of chemistry at Scripps Research. “We think the kind of reactions we’ve described are probably what could have happened on early Earth.” Krishnamurthy is the lead author of the new paper that was published in the journal Nature Chemistry on July 28, 2022.
In addition to giving scientists insight into the chemistry of the early Earth, the newly discovered chemical reactions are also useful in certain manufacturing processes. For example, in the generation of custom-labeled biomolecules from inexpensive starting materials.
Earlier this year, Krishnamurthy’s team showed how cyanide can enable the chemical reactions that turn prebiotic molecules and water into basic organic compounds required for life. This one worked at room temperature and in a wide pH range, unlike previously proposed reactions. The scientists wondered whether, under the same conditions, there was a way to generate amino acids, which are more complex molecules that compose proteins in all known living cells.
In cells today, amino acids are generated from precursors called α-keto acids using both nitrogen and specialized proteins called enzymes. Scientists have discovered evidence that α-keto acids likely existed early in Earth’s history. However, many researchers have hypothesized that before the advent of cellular life, amino acids must have been generated from completely different precursors, aldehydes, rather than α-keto acids, since enzymes to carry out the conversion did not yet exist. But that idea has led to debate about how and when the switch occurred from aldehydes to α-keto acids as the key ingredient for making amino acids.